Liberated Amino Acids Research Articles

Keratinases produced by Chryseobacterium proteolyticum FGNn and Pseudomonas aeruginosa GNFx liberated amino acids from poultry feathers

AbstractThe agro-industrial sector generates diverse waste that requires effective handling to mitigate economic loss and pollution. Consequently, this study assessed bacterial isolates from poultry dumpsites for feather decomposition and keratinase production capacity. The protein hydrolysates generated from feather dismemberment by two bacteria identified as Chryseobacterium proteolyticum FGNn (accession no. MW165478) and Pseudomonas aeruginosa GNFx (accession no. MW165479) were profiled for amino acids composition. The biochemical properties of the bacteria-associated keratinases were determined. Initial keratinase production (with percentage feather degradation), demonstrated by the isolates, was 693.63 ± 62.99 U/mL (81%) and 619.09 ± 37.28 (76%) against FGNn and GNFx, respectively. At optimized process conditions, C. proteolyticum and P. aeruginosa extracellular keratinase production was 1756.36 ± 2.57 U/mL at 72 h and 2055.45 ± 50.14 U/mL at 96 h, respectively. Analysis of the feather hydrolysates showed a relatively high abundance of arginine (3.18%) and glycine (3.26%) for FGNn and glutamic acid (6.05%), serine (3.31%), aspartic acid (4.74%), glycine (3.71%), alanine (3.43%), valine (3.09%), and leucine (3.23%) for GNFx. The keratinolytic proteases showed pH and temperature optima of 8.0 and 50°C against FGNn, and 8.0 and 60°C against GNFx. GNFx keratinase was thermostable, displaying a half-life time of more than 60 min at 80°C. In addition, GNFx keratinolytic enzyme was chemical agent tolerant post-treatment. The findings underlined the significance of C. proteolyticum FGNn and P. aeruginosa GNFx as suitable in the valorisation of keratinous biomass. Also, the robust stability profile of GNFx keratinase highlights its prospects in green technology.

Crick's Adaptor Hypothesis and the Discovery of Transfer RNA: Experiment Surpassing Theoretical Prediction

Historically, hypotheses failed in most cases to correctly forecast the workings of complex biological systems. Francis Crick’s adaptor hypothesis, however, stands out as an exceptional case of a confirmed abstract prediction. This hypothesis presciently anticipated the existence of RNA adaptors that function as bridges between amino acids and the chemically different nucleic acid template for proteins. Crick conjectured that the adaptors are enzymatically charged with cognate amino acids, they bind to complementary protein-coding nucleic acid, and their liberated amino acids are incorporated into growing protein chains. Independently from and concomitantly with Crick’s hypothesis, Mahlon Hoagland and Paul Zamecnik conducted experiments with no guiding theory that culminated in discoveries of the actual adaptors, transfer RNA (tRNA) molecules, and their amino acids charging enzymes. This paper traces the parallel histories of Crick’s adaptor hypothesis and of the experimental discovery of tRNA and compares their relative impacts on the scientific community. Remarkably, despite the brilliance of Crick’s confirmed prognostication, it had marginal impact on practicing scientists. Conversely, Hoagland and Zamecnik’s experimental discoveries and their evidence-based model of protein synthesis had immediate and enduring impact. I discuss possible explanations for the different impacts of the theoretical prediction and experimental identifications of the same entities.

Crick's Adaptor Hypothesis and the Discovery of Transfer RNA: Experiment Surpassing Theoretical Prediction

Historically, hypotheses failed in most cases to correctly forecast the workings of complex biological systems. Francis Crick’s adaptor hypothesis, however, stands out as an exceptional case of a confirmed abstract prediction. This hypothesis presciently anticipated the existence of RNA adaptors that function as bridges between amino acids and the chemically different nucleic acid template for proteins. Crick conjectured that the adaptors are enzymatically charged with cognate amino acids, they bind to complementary protein-coding nucleic acid, and their liberated amino acids are incorporated into growing protein chains. Independently from and concomitantly with Crick’s hypothesis, Mahlon Hoagland and Paul Zamecnik conducted experiments with no guiding theory that culminated in discoveries of the actual adaptors, transfer RNA (tRNA) molecules, and their amino acids charging enzymes. This paper traces the parallel histories of Crick’s adaptor hypothesis and of the experimental discovery of tRNA and compares their relative impacts on the scientific community. Remarkably, despite the brilliance of Crick’s confirmed prognostication, it had marginal impact on practicing scientists. Conversely, Hoagland and Zamecnik’s experimental discoveries and their evidence-based model of protein synthesis had immediate and enduring impact. I discuss possible explanations for the different impacts of the theoretical prediction and experimental identifications of the same entities.

Macropinocytosis: the big drinker behind cancer cell self-consumption

ABSTRACT Poorly vascularized tumors embedded within a thick desmoplastic stroma, like pancreatic ductal adenocarcinoma (PDAC), are nutritionally stressed. Such tumors are also hypoxic and rely on a number of adaptive responses, including macroautophagy/autophagy and macropinocytosis (MP), to support their bioenergetic needs. Whereas autophagy enables starved cells to recycle intracellular macromolecules via lysosomal degradation and use the liberated amino acids (AA) to fuel their metabolism, MP allows cells to take up extracellular proteins via fluid-phase endocytosis and use them as an energy source. However, how any MP-enabled organism, including the prototypical cancer cell, coordinately regulates and balances autophagy and MP is not fully understood. We recently found that inhibition of autophagy results in upregulation of MP, which enables cancer cells to overcome autophagy deficiency and continue to support their bioenergetic demands. The NFE2L2/NRF2-driven induction of MP-related genes (MRGs) is responsible for the upregulation of MP in autophagy inhibited, hypoxic, and oxidatively stressed-exposed cancer cells. Concurrent autophagy and MP blockade effectively cuts off the cancer cell’s nutrient and supplies, leading to rapid tumor regression. These findings suggest MP to be an important target in cancer treatment and that shutting off the energy spigot is a promising therapeutic strategy. Abbreviations AA: amino acids; ADCs: autophagy deficient-cells; AI: autophagy inhibition; ALB: albumin; CHUK/IKKα: component of inhibitor of nuclear factor kappa B kinase complex; CQ: chloroquine; ECM: extracellular matrix; HCQ: hydroxychloroquine; MI: MP inhibition; MP: macropinocytosis; MRGs: MP-related genes; MRPs: MP-related proteins; PDAC: pancreatic ductal adenocarcinoma.

Protein Precipitation to Remove Carbohydrates that Interfere in Protein-Bound Tryptophan Quantification in Soybean Seeds

Tryptophan is one of the nine essential amino acids in humans that can only be obtained through diets and supplements. It is a precursor to many biological processes, such as serotonin, melatonin, kynurenin, and niacin (nicotinamide) vitamin synthesis. The content of tryptophan in foods, such as soybean is an important indicator of nutritional value. Therefore, accurate quantification of tryptophan in soybean is crucial to soybean nutritional improvement. Quantification of soybean protein-bound amino acids first involves acid hydrolysis of total protein to liberate amino acids. However, tryptophan quantification following acid hydrolysis is difficult or impossible due to its reactions with soybean carbohydrates. Therefore, removal of carbohydrates from soy proteins prior to acid hydrolysis is necessary. In this study, we compared four common protein precipitation methods (i.e., methanol, acetonitrile, acetone, and trichloroacetic acid (TCA) protein precipitation methods) to determine the best method to separate soy proteins from carbohydrates, and concluded that acetone provided the highest recovery of soy proteins. Tryptophan content in the precipitated proteins was determined after acid hydrolysis of the proteins using liquid chromatography–tandem mass spectrometry multiple reaction monitoring (LC–MS/MS–MRM). No significant difference in the tryptophan content was found among proteins precipitated with methanol, acetonitrile, and TCA, suggesting that these precipitated proteins have similar compositions. A slightly lower, but statistically significant tryptophan content was found in the acetonitrile-precipitated proteins, suggesting that these proteins contain slightly higher glycosylated proteins.

A Subcritical Water Extractor Prototype for Potential Astrobiology Spaceflight Missions

AbstractA top‐level NASA exploration goal is the search for signs of life beyond Earth. Molecular biosignatures can be sought via in situ organic chemical analyses of samples collected from planetary bodies. Current spaceflight‐ready technologies lack the required sensitivity to perform these analyses on key polar organic species primarily due to the low efficiency of transferring these molecules from natural samples into chemical instrumentation. One promising approach to improve the liberation of these molecules from sample matrices prior to analysis is through the use of liquid extraction, in which organic molecules are dissolved in heated, pressurized water. This process has never been performed on a spaceflight mission. As part of instrument maturation efforts, we describe the development of the first spaceflight prototype of a fully automated subcritical water extractor designed to provide this essential functionality on a potential future planetary mission. The prototype extractor was mounted on a Mars test rover platform and successfully operated remotely in the Atacama Desert, Chile. Samples acquired by the rover's drill and sample acquisition/delivery system were remotely transferred to the extractor inlet funnel, and all subsequent extractor operations were performed automatically. To validate the instrument and demonstrate its suitability as a front‐end unit for an organic analyzer, we tested low‐bioload Atacama Desert soil extracts for amino acid content using capillary electrophoresis coupled to laser‐induced fluorescence. We show that hot extraction under subcritical conditions is required to liberate amino acids from the sample, as no amino acids were found in the extract produced at room temperature.

AMINO ACIDS PRODUCTION BY PROTEOLYTIC MUCOR MUCEDO STRAIN SEE1 ON THE OPTIMIZED FERMENTATION MEDIUM

The present study has been conducted to isolate the potential fungal isolates in proteolysis process. One isolate showed high activity in protease production, being Mucor sp. Morphological and microscopical studies, as well as 18S rRNA sequence confirmed that this isolate is identified as Mucor mucedo strain SEE1 and sequencing product was deposited in the GenBank database under the accession number KP736529. Optimization of protease production during Plackett-Burman and central composite designs has been carried out, with six nutritional variables. Glucose and casein were significantly superior to other variables in protease production. Moreover, an overall 3.36-fold increase in protease production has been obtained by Placket-Burman. However, 1.14-fold increase was found in central composite design. On the other hand, during the fermentation process in optimized medium, liberated amino acids has been determined (µg/ml), where histidine came in the first order (1155.3) followed by lysine (897.4), tyrosine (634), arginine (580) and isoleucine (580), respectively. However, cysteine was found in less appreciable amount (36).

Determination of the mode of action of enterolysin A, produced by Enterococcus faecalis B9510

The current study aimed to visualize the damage caused by enterolysin A to the cells of sensitive strains and to find out cleavage site within the peptidoglycan moiety of bacterial cell walls. Enterolysin A produced by a local isolate, Enterococcus faecalis B9510 was found to rapidly kill cells of the sensitive strain Lactococcus lactis ssp. cremoris 2144 during 120 min of treatment as compared to the untreated control where no such effect was observed. Transmission electron microscopy of the enterolysin A-treated cells revealed leaking of the cytoplasmic contents ultimately resulting in complete lysis of cell walls. To find the cleavage site, purified cell walls of L. lactis ssp. cremoris 2144, Pediococcus pentosaceus 43201 and Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 were treated with enterolysin A, and liberated amino acids were derivatized for N and C terminals and analysed using thin layer chromatography on silica gel with isopropanol as solvent. The results showed that enterolysin A cleaves the peptide bonds at two locations within peptidoglycan subunits. The first location is between L-alanine and D-glutamic acid of the stem peptide and the other location is between L-lysine of the stem peptide and D-aspartic acid of the interpeptide bridge. Enterolysin A cleaves the peptide bonds within the stem peptide as well as in the interpeptide bridge of Gram-positive bacterial cell walls. This gives a possible reason for the broad spectrum of enterolysin A activity. This is the first report identifying the cleavage site of enterolysin A within the cell walls of sensitive bacteria. This will help in identifying potential applications for enterolysin A.

The Potential Role of Dietary Intake in Explaining Postoperative Muscle Loss in Total Knee Arthoplasty (TKA)

Post-operative muscle loss has been identified as the greatest contributor to osteoarthritis patients’ long-term strength deficits, explaining 77% of muscle weakness one to three years after total knee arthroplasty (TKA) for the treatment of osteoarthritis in the knee. Essential amino acid supplementation may help reduce atrophy, but other factors could have an equally influential role. Patients’ food intake could likewise affect atrophy, and thus dietary intake must be measured in order to determine whether essential amino acids reduce muscle loss following TKA. Subjects with a minimal dietary intake could exacerbate muscle loss because fasting causes the body to break down skeletal muscle protein to liberate amino acids for use as gluconeogenic precursors in the liver. As a result, individuals with different diets may experience differing degrees of muscle atrophy. This investigation seeks to test the hypothesis that higher rates of muscle atrophy in subject groups could be explained by comparatively poorer dietary intake. For this study, subjects completed a total of three 24-hour food logs before surgery, then two, and six weeks post-TKA. During these periods, bilateral quadriceps muscle volume was determined using magnetic resonance imaging (MRI). Baseline and six-week whole-body dual-energy X-ray (DEXA) scans were also performed to compare changes in lean tissue and fat mass. Data collected indicated there was no significant difference in dietary intake between the control group and treatment group, suggesting that any muscle saved in the treatment group was a result of essential amino acid supplementation.

Isolation and activation of collagenase from fish processing waste

Collagenase was isolated from fish waste (a mixture of haddock, herring, ground fish and flounder) using a Tris-buffer system. The proteins in the crude extract were precipitated using ammonium sulfate (40% - 80%) and purified with gel-filtration chromatography using Sephadex G-100. The results showed that the collagenase enzyme was produced as a latent enzyme and was activated with bovine trypsin and potassium thiocyanate (KSCN). The enzyme activity was affected by pH and temperature. Optimal enzyme activities were found at 35?C and a pH of 7.5 when insoluble collagene type I was used as substrate and the liberated amino acids were measured in relation to L-leucine in the presence of ninhydrin. The enzyme activity was completely inhibited by the action of ethylenediaminetetraacetic acid (EDTA) suggesting that the collagenase enzyme isolated from the fish waste is a metalloproteinase enzyme requiring metal ions for enzyme activity. Dialysis against KSCN decreased the enzyme total activity and increased its specific activity. Sodium dodecyl sulphate polyacryla-mide gel electrophoresis (SDS-PAGE) indicated that the purified procollagenase enzyme have only one band at molecular weight of 50 kilodaltons (kDa). When the enzyme was cleaved with trypsin, it was found to consist of two subunits: a large unit with a molecular weight of 50 kDa and a small unit with a molecular weight of 10 kDa.

Amino acid analysis.

Amino acid analysis is used to determine the amino acid content of amino acid-, peptide- and protein-containing samples. With minor exceptions, proteins are long linear polymers of amino acids connected to each other via peptide bonds. The first step of amino acid analysis involves hydrolyzing these peptide bonds. The liberated amino acids are then separated, detected, and quantified. The method was first developed by Moore, Stein and coworkers in the 1950s using HCl acid hydrolysis, and, despite considerable effort by many workers, the basic methodology remains relatively unchanged. This unit provides an overview and strategic planning for amino acid analysis, discussing a range of methodologies and issues. In addition, several common methods used for analysis of L-amino acids are described in detail, including: HCl acid hydrolysis, performic acid oxidation for methionine and cysteine analysis, base hydrolysis for tryptophan analysis, analysis of free amino acids, and analysis of reactive lysine.

Escherichia coli, an Intestinal Microorganism, as a Biosensor for Quantification of Amino Acid Bioavailability

In animal diets optimal amino acid quantities and balance among amino acids is of great nutritional importance. Essential amino acid deficiencies have negative impacts on animal physiology, most often expressed in sub-optimal body weight gains. Over supplementation of diets with amino acids is costly and can increase the nitrogen emissions from animals. Although in vivo animal assays for quantification of amino acid bioavailability are well established, Escherichia coli-based bioassays are viable potential alternatives in terms of accuracy, cost, and time input. E. coli inhabits the gastrointestinal tract and although more abundant in colon, a relatively high titer of E. coli can also be isolated from the small intestine, where primary absorption of amino acids and peptides occur. After feed proteins are digested, liberated amino acids and small peptides are assimilated by both the small intestine and E. coli. The similar pattern of uptake is a necessary prerequisite to establish E. coli cells as accurate amino acid biosensors. In fact, amino acid transporters in both intestinal and E. coli cells are stereospecific, delivering only the respective biological l-forms. The presence of free amino- and carboxyl groups is critical for amino acid and dipeptide transport in both biological subjects. Di-, tri- and tetrapeptides can enter enterocytes; likewise only di-, tri- and tetrapeptides support E. coli growth. These similarities in addition to the well known bacterial genetics make E. coli an optimal bioassay microorganism for the assessment of nutritionally available amino acids in feeds.

In vitro degradation of oxytocin by pregnancy serum, placental subcellular fractions and purified placental aminopeptidases.

The degradation of oxytocin (formula; see text) by human placental particulate and soluble fractions, pregnant and non-pregnant sera, and purified enzymes such as microsomal placental leucine aminopeptidase (P-LAP), retroplacental serum P-LAP and placental post-proline endopeptidase, was studied by measuring liberated amino acids with a high performance liquid chromatograph (HPLC). While the placental particulate fraction degraded oxytocin almost completely into single amino acid and amide, the placental soluble fraction did not liberate any amino acid and amide. Purified retroplacental P-LAP liberated Tyr2, Ile3, Gln4 and Asn5 from the cyclic structure of oxytocin actively. Pregnancy serum containing the retroplacental P-LAP liberated also these amino acids and amides. Purified microsomal P-LAP liberated Leu8 in addition to these amino acids and amides. Although purified placental post-proline endopeptidase or porcine kidney leucine aminopeptidase (LAP) could not liberate any amino acid and amide from oxytocin, the combination of the post-proline endopeptidase with porcine kidney LAP or with placental microsomal P-LAP actively liberated all amino acids and amides detectable by HPLC. When the ratio of amino acid liberation velocity to LAP activity measured with leu-p-nitroanilide was calculated, the ratios for cyclic amino acids such as Tyr2 and Ile3 were high with the placental particulate fraction, the mixture of post-proline endopeptidase and microsomal P-LAP, retroplacental P-LAP, and pregnancy serum. The ratio for Leu8 was high with the placental particulate fraction and the mixture of post-proline endopeptidase and microsomal P-LAP.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro degradation of opioid peptides by human placental aminopeptidase M.

The degradation of opioid peptides by human placental aminopeptidase M was studied by measuring liberated amino acids by high performance liquid chromatography. The purified placental aminopeptidase M actively degraded Met-enkephalin (Met-Enk) and Leu-enkephalin (Leu-Enk) completely into constituent 5 amino acids. The activities as a function of tyrosine liberation were observed for Met-Enk followed by Leu-Enk, beta-neoendorphin, dynorphin, and beta-endorphin.

Wheat gluten amino acid composition analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection

A simple accurate method for determining amino acid composition of wheat gluten proteins and their gliadin and glutenin fractions using high-performance anion-exchange chromatography with integrated pulsed amperometric detection is described. In contrast to most conventional methods, the analysis requires neither pre- or post-column derivatization, nor oxidation of the sample. It consists of hydrolysis (6.0 M hydrochloric acid solution at 110 °C for 24 h), evaporation of hydrolyzates (110 °C), and chromatographic separation of the liberated amino acids. Correction factors ( f) accounted for incomplete cleavage of peptide bonds involving Val ( f = 1.07) and Ile ( f = 1.13) after hydrolysis for 24 h and for Ser ( f = 1.32) losses during evaporation. Gradient conditions including an extra eluent (0.1 M acetic acid solution) allowed multiple sequential sample analyses without risk of Glu contamination on the anion-exchange column. While gluten amino acid compositions by the present method were mostly comparable to those obtained by a conventional method involving oxidation, acid hydrolysis and post-column ninhydrin derivatization, the latter method underestimated Tyr, Val and Ile levels. Results for the other amino acids obtained by the different methods were linearly correlated ( r > 0.99, slope = 1.03).

Adaptive Responses by Mouse Early Embryos to Maternal Diet Protect Fetal Growth but Predispose to Adult Onset Disease1

Poor maternal nutrition during pregnancy can alter postnatal phenotype and increase susceptibility to adult cardiovascular and metabolic diseases. However, underlying mechanisms are largely unknown. Here, we show that maternal low protein diet (LPD), fed exclusively during mouse preimplantation development, leads to offspring with increased weight from birth, sustained hypertension, and abnormal anxiety-related behavior, especially in females. These adverse outcomes were interrelated with increased perinatal weight being predictive of later adult overweight and hypertension. Embryo transfer experiments revealed that the increase in perinatal weight was induced within blastocysts responding to preimplantation LPD, independent of subsequent maternal environment during later pregnancy. We further identified the embryo-derived visceral yolk sac endoderm (VYSE) as one mediator of this response. VYSE contributes to fetal growth through endocytosis of maternal proteins, mainly via the multiligand megalin (LRP2) receptor and supply of liberated amino acids. Thus, LPD maintained throughout gestation stimulated VYSE nutrient transport capacity and megalin expression in late pregnancy, with enhanced megalin expression evident even when LPD was limited to the preimplantation period. Our results demonstrate that in a nutrient-restricted environment, the preimplantation embryo activates physiological mechanisms of developmental plasticity to stablize conceptus growth and enhance postnatal fitness. However, activation of such responses may also lead to adult excess growth and cardiovascular and behavioral diseases.

A Role for Milk Proteins and their Peptides in Cancer Prevention

A role for the amount and type of dietary protein in the etiology of cancer has not been studied extensively. Nevertheless, there is no compelling evidence from epidemiological studies to indicate that protein, at levels usually consumed, is a risk factor for cancer. On the other hand, animal studies suggest that certain peptides and amino acids derived from dietary proteins may influence carcinogenesis. The predominant protein in milk, casein, its peptides, but not liberated amino acids, have antimutagenic properties. Animal models, usually for colon and mammary tumorigenesis, nearly always show that whey protein is superior to other dietary proteins for suppression of tumour development. This benefit is attributed to its high content of cystine/cysteine and gamma-glutamylcyst(e)ine dipeptides, which are efficient substrates for the synthesis of glutathione. Glutathione is an ubiquitous cellular antioxidant that directly or through its associated enzymes destroys reactive oxygen species, detoxifies carcinogens, maintains proteins in a reduced state and ensures a competent immune system. Various experiments showed that tumour prevention by dietary whey protein was accompanied by increased glutathione levels in serum and tissues as well as enhanced splenic lymphocyte proliferation, phagocytosis and natural killer, T helper and cytotoxic T cell activity. Whey protein components, beta-lactoglobulin, alpha-lactalbumin and serum albumin were studied infrequently, but results suggest they have anticancer potential. The minor component lactoferrin has received the most attention; it inhibits intestinal tumours and perhaps tumours at other sites. Lactoferrin acts by induction of apoptosis, inhibition of angiogenesis, modulation of carcinogen metabolising enzymes and perhaps acting as an iron scavenger. Supplementing cows with selenium increases the content of selenoproteins in milk, which on isolation inhibited colon tumorigenesis in rats.

Molecular and functional characterization of Lactobacillus sanfranciscensis strains isolated from sourdoughs

Fifty isolates of Lactobacillus sanfranciscensis from Italian sourdoughs were identified and typed by a polyphasic approach which included genotypic and phenotypic criteria. Genotypic diversity was characterized by Ribosomal Intergenic Spacer Analysis (RISA) of PCR amplified 16S–23S rDNA spacer region, denaturing gradient gel electrophoresis (DGGE) of PCR amplified rpoB (β subunit of RNA polymerase) gene, and rep-PCR (PCR amplification of repetitive bacterial DNA elements) analyses. The RISA analysis produced a unique electrophoretical profile of four bands (ranging from 300 to 600 bp) for all L. sanfranciscensis isolates. The DGGE analysis of rpoB gene allowed the subdivision of isolates in four clusters. The resolution found by using rep-PCR with primers BOXA1R and REP1R-I/REP2-I allowed the widening of the level of isolates heterogeneity. Phenotypic diversity was evaluated by Biolog System and characterization of several technological traits (e.g., acidification kinetics, proteinase and peptidase activities). L. sanfranciscensis isolates used a large varieties of carbon sources such as dextrin, d-fructose, l-fucose, α- d-glucose, maltose, palatinose, l-rhanmose, l- and d, l-lactic acids and l-methionine. The acidification activity and related quotient of fermentation, and the peptidase (PepN, PepV, PepT, PepI, PepX, PepQ and PepR) activities markedly varied among strains. The same was found concerning the capacity to liberate amino acids during sourdough fermentation. This study could be considered as an example of a computerized analysis of the genotypic and phenotypic traits to reliably and rapidly differentiate sourdough isolates. Although some L. sanfranciscensis isolates combined several technological traits, the association of more selected strains seemed to be a requisite to get optimal sourdough characteristics.

Seasonal patterns of nucleic acid concentrations and amino acid profiles of Parapenaeus longirostris (Crustacea, Decapoda): relation to growth and nutritional condition

The present work describes the seasonal changes in nucleic acid concentrations and amino acid profiles in the muscle of juvenile Parapenaeus longirostris and their relation to growth and nutritional condition. RNA content varied significantly between seasons, being the highest values attained in spring and the lowest in winter (p 0.05). In opposition, during this period a significant decrease in the free amino acid content (FAA) was observed (p < 0.05); a higher percentage of decrease was attained in free non-essential (FNEAA – 42.9) in comparison to free essential amino acids (FEAA – 40.2). The significant increase in RNA and TAA contents from winter to spring may be related with protein synthesis. On the other hand, the lowest values obtained in winter may be due to a reduction in feeding activity; in this period the muscle protein must be progressively hydrolysed, which is evident with the higher FAA content. The liberated amino acids enter FAA pool and become available for energy production. In conclusion, it was evident that the seasonal cycle in activities such as feeding and growth with nucleic acids and amino acid analyses was noticed.

RNA, DNA and protein concentrations and amino acid profiles of deep-sea decapodAristeus antennatus: An indication for seasonal variations of nutrition and growth

Seasonal changes in nucleic acid concentrations and amino acid profiles in the muscle of juvenile Aristeus antennatus were investigated. RNA content, RNA:DNA and RNA:protein ratios varied significantly between seasons (p < 0.05), being the lowest and the highest values obtained in winter and spring/summer. A significant variation in the total amino acid content (TAA) from winter to summer was observed (p < 0.05). In fact, during this period a significant percent of increase in total non- (NEAA; 20.2%) and essential amino acids (EAA, 18.7%) contents occurred. Concomitantly, a significant decrease in the free amino acid (FAA) content from winter to summer was observed. A higher percentage of decrease with free essential amino acids (FEAA; 56.6%) in comparison to free non-essential amino acids (FNEAA; 34.2%) was attained. The significant increase in RNA and TAA contents from winter to summer may be related with protein synthesis. On the other hand, the lowest values obtained in winter may be due to a reduction in feeding activity; in this period the muscle protein must be progressively hydrolysed, which is evident with the higher FAA content. The liberated amino acids enter FAA pool and become available for energy production.